1. Field of the Invention
The present invention generally relates to a compound water meter of the type having main and secondary meter devices and a switch-over valve for controlling switching in and out of the main meter device and, more particularly, is concerned with switch-over valve having pivot axle articulated closure wings extending across the throughflow cross section of the compound water meter.
2. Description of the Prior Art
Compound water meters are used in cases in which the measuring range of a simple meter is not sufficient to cover all throughflows which might occur. These compound water meters include a large water meter as the main meter device, a house water meter as a secondary meter device, and a switch-over valve. The switch-over valve controls the switching in and out of the main meter device, which as a rule, is realized as a Woltmann meter and assumes volume measurement only for relatively large predetermined throughflows in addition to the secondary meter device.
Compound water meters are known in which the switchover valve is implemented as a weight-loaded hinged flap, as disclosed in U.S. Pat. No. 4,100,800, which upon being completely opened gates the through-flow cross section. The weight-loaded hinged flap swivels in the process about a pivot being laterally offset from the throughflow cross section. The disadvantage of this configuration is that for the pivoting of the hinged flap to occur much volume is required which leads to long and heavy compound water meters. Furthermore, complicated profile seals are required for the valve seat.
Furthermore are known compound water meters of the above-cited type, for example from German patent document Nos. DE 37 32 703 A1, DE 37 40 531 A1 or DE 39 24 147 C1. In the case of these meters, the closure member of the switch-over valve is guided translationally on an axle located centrally in the direction of flow, and loaded with a spring which presses it counter to the direction of flow into contact on a valve seat. Starting at a predetermined throughflow quantity, the closure member moves away from the valve seat while overcoming the spring force and is displaced in the direction of flow. Thereby an annular throughflow cross section is enabled.
Switch-over valves structured in this way have a smaller space requirement compared to the above-cited prior art but are still rather long, which has a negative effect on the length and the weight of the compound water meter. In addition, these known switch-over valves are complicated and thus expensive since they are built from a relatively large number of components and require profile seals for their correct functioning. Further disadvantages are that in their open position they constrict the flow cross section and consequently cause pressure losses, which are not insignificant, and are only suitable as check valves to a limited extent.